Composition containing divalent manganese ion and method for preparing the same

ABSTRACT

There is provided a composition containing divalent manganese and a method for preparing the compound. The compound is stable but has good activity and reactivity to be able to use as a deodorizer.

This application is a continuation of application Ser. No. 07/827,498,filed on Jan. 30, 1992, now abandoned, which is a continuation ofapplication Ser. No. 07/352,253 filed on May 16, 1989, now abandoned.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates to a composition containing a divalentmanganese ion and a method for preparing said composition.

(2) Description of the Prior Art

Manganese takes several oxidation forms, such as divalent, trivalent,tetravalent, hexavalent, and heptavalent. In particular, permanganate,in which manganese takes a heptavalent state, exhibits high oxidationpower, resulting in it being extensively utilized as an agent forchemical synthesis, analysis, and the like.

Unfortunately, permanganate involves colored property and some safetyconcerns, due to its high oxidation power. Accordingly, it isdisadvantageous in that when it is to be used in the home, it must becarried on a substrate, such as activated carbon.

The most stable of the manganates contain a divalent manganese ion.However, the reactivity of the divalent manganate is low, so that itsuse range is quite restricted. For example, in a fixing reaction, due tothe formation of manganese sulfide by reacting sulfide in the categoryof an odorous material such as hydrogen sulfide, methyl mercaptan,methyl disulfide, or the like with a divalent manganese compound, theion-dissociation of the sulfide is increased as its pH changes fromneutrality to alkalinity, such that it is necessary to provide thesulfide with a base effect. However, this causes its divalent manganeseion to be insoluble, leading to the formation of manganese hydroxidewhile exhibiting a chelate effect, which does not contribute to itsreactivity.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a novel manganesecomposition capable of exhibiting improved stability and safety and highreactivity while eliminating the above-described disadvantage of aconventional manganese compound.

The above and other objects, features, and advantages of the inventionwill become apparent in the following detailed description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graphic representation showing relationships between amanganese (II)-ascorbic acid composition and its ammonia-adsorptioncapability, and

FIG. 2 is a graphic representation showing relationships between amanganese (II)-citric acid composition and its ammonia-adsorptioncapability.

DETAILED DESCRIPTION OF THE INVENTION

The inventor, in working to achieve the above-described object, foundthat the addition of ascorbic acid, which is essential to the human bodyto a solution containing a water-soluble manganese (II) salt for thepurpose of activating a divalent manganese ion, improved the chemicalreactivity of manganese (II). It was also found that the addition ofascorbic acid to manganese (II) at an optimum ratio followed by theaddition of a material, such as, for example, citric acid or the like,which readily forms a water-soluble complex in cooperation withmanganese (II), thereto for the purpose of further improving a chemicalreactivity of manganese (II) and maintaining stability of a manganese(II) composition, leads to a composition that exhibits better reactivityand can be effectively used for removing odor. The present invention hasbeen made in view of the above facts.

More particularly, the present invention provides first a manganese (II)composition comprising divalent manganese ion and at least one acidcomponent selected from a group consisting of ascorbic acid,oxypolybasic acids, or their salts.

The present invention also provides for a method of preparing acomposition containing manganese (II) comprising mixing at least oneacid component selected from a group consisting of ascorbic acid,oxypolybasic acids, or their salts in an aqueous solution of divalentmanganese ion.

In the present invention, the ratio of the acid ingredient to thedivalent manganese ion is not limited to a specific range, as long asthe composition of the present invention mainly consists of the divalentmanganese ion. Nevertheless, the molar ratio of the acid ingredient((L,D-) ascorbic acid or oxypolybasic acid) to the manganese (II) saltor compound is preferably 0.1 to 1.0, more preferably 0.25 to 0.75 (ifascorbic acid is used, it is in an amount 19 to 57 percent by weightbased on the manganese (II) compound). Preparation of such a compositionmay be carried out by adding a suitable amount of the acid ingredient toan aqueous solution of the manganese (II) and dissolving the former inthe latter.

When oxypolybasic acid is used as the acid ingredient, a molar ratio ofthe acid ingredient to the manganese (II) salt is preferably 0.5 to 1.0(the amount of oxypolybasic acid to the manganese (II) compound being 45to 91 percent by weight).

The manganese (II) compounds suitable for use in the present inventioninclude both inorganic and organic manganese (II) compounds.Water-soluble manganese (II) salts such as, for example, manganese (II)chloride, manganese (II) nitrate, manganese (II) sulfate, manganese (II)acetate, manganese (II) thiocyanate, and the like may be used for thispurpose. A concentration of an aqueous solution of the manganese (II)salt is not limited to a specific range as long as the concentration isincluded in the range of its solubility. However, it is preferably inthe range of 10 to 25% by weight.

Ascorbic acids that may be used as the acid ingredient added to theaqueous manganese (II) solution in the present invention includeL-ascorbic acid, which is generally known as vitamin C. D-ascorbic acidis referred to as D-araboascorbic acid or D-erythrobic acid, and it isoften used for various purposes because it is readily synthesized,although it exhibits poor physiological activity compared with vitaminC. D-ascorbic acid likewise may be used as the acid ingredient in thepresent invention. These ascorbic acids each may be used in the form ofits alkali metal salt, such as sodium and potassium ascotbate, or itsammonium salt.

Oxypolybasic acids that may be used in the present invention includetartronic acid, malic acid, gluconic acid, citric acid, oxybenzoic acid,salicylic acid, their alkaline metal salts, their ammonium salts, andthe like. Of the oxypolyacids, citric acid is conveniently used in viewof its utility, such as its low cost and the like. The above-exemplifiedoxypolybasic acids each form coordinate bonding or chelate bonding withmanganese (II), resulting in a composition stable in an aqueoussolution.

In the present invention, it is more preferable to coexist theoxypolybasic acid in the manganese (II)-ascorbic acid system.

Such use of the oxypolybasic acid in combination with the ascorbic acidcauses a solution of the manganese (II) composition to satisfactorilyreact with sulfide ions in a gas-liquid contact reaction for contactingthe solution with odorous gas in air, even when the pH of the solutionis in the acid region, resulting in the removal of a sulfur-containingmaterial. Such function of the solution is promoted corresponding toneutral fixing of ammonia.

In the present invention, when NaCl or KCl is added in an amount of 3%to 7% by weight to the solution, the ion dissociation is retarded bybeing accompanied with the increase of ion density, and the oxidation ofascorbic acid due to the dissolved oxygen in the aqueous solution isalso retarded to improve the stability of the solution.

Further, the addition of a reducing agent such as N₂ S₂ O₄, Na₂ SO₃, andNa₂ S₂ O₃ in an amount of 0.1% to 0.2% by weight to the solution of thepresent invention is effective to prevent its stability fromdeterioration which is caused by the presence of an oxidative material.In particular, the reducing agent is excellent in preventing theoxidation of ascorbic acid. The amount addition below 0.1% is lesseffective, and when it exceeds 0.2% a negative effect such as generationof gas occurs.

Use of the manganese (II) composition of the present invention is notlimited to any specific form. It may be used in the form of itssolution. Alternatively, it may take a solid form, which may be obtainedby spray-drying or lyophilization. The solid composition may be used ina manner to be mixed with resin or carried on a porous substrate such aspaper, activated carbon, or the like by impregnation. The amount of thecomposition to be carried on the substrate by impregnation may besuitably varied depending on its application. The amount of thecomposition used in the form of a solution is generally in a range of10-70% by weight, although it is varied depending on its application.

The mechanism of the reaction by the manganese (II) compound of thepresent invention has not been made clear. However, it is supposed that,for example, a reaction of the compound with sulfide would be carriedout in such a manner that a chelate compound of manganese (II) takes inan oxygen molecule from air and then converts it into active oxygen, sothat sulfide caught by the manganese (II) may be oxidized with theactive oxygen. A composition free of manganese (II) and consisting ofonly the acid ingredient, such as ascorbic acid or the like, fails toexhibit such a function because of its weak acidity.

In the composition of the present invention, it is not necessary thatthe manganese (II) ion component bonds with the acid component from thebeginning as long as they bond to each other when the composition isused. Thus the composition of the present invention embraces a solemixture of the components not bonded to each other.

In order to cause the composition of the present invention to moreefficiently carry out the reaction, water preferably coexists. For thesame purpose, a small amount of alcohol may be added.

The manganese (II) composition of the present invention exhibitssatisfactory stability, activity, and reactivity. Such featuredproperties of the composition permit it to be used most preferably as adeodorizer capable of removing ammonia, trimethylamine, sulfides, suchas hydrogen sulfide, methyl mercaptan and methyl disulfide and the like.It is known that a certain metal complex is substantially colored anddeteriorated in stability due to oxidation by oxygen molecules in theair. However, the composition of the present invention is substantiallyfree from discoloration and deterioration in performance, even when itis left standing in the form of a solution for as long as about twomonths. Also, it does not cause any change in color, even when it isdried. Further, the composition is not substantially colored even afterit reacts with a smelly material. Thus, it will be noted that thecomposition of the present invention exhibits the noteworthy advantagethat it is free from coloring even when it is used as an impregnatingmaterial or substrate.

The manganese (II) composition of the present invention that exhibitssuch properties as described above would be extensively used as not onlya substrate for removing odors, but as a culture medium forbioindustries, as a functional food agent for human consumption, as acatalyst for oxidation of organic substance, and as a material for anindustry in which manganese (II) is used as a raw material. In suchapplications, the adjustment of the pH of the composition of the presentinvention from 2 to 6 by the addition of weak alkali causes theadvantage of the composition to be more promoted, because thedissociation of sulfide may be readily carried out.

The invention will be described in further detail referring to examples.

EXAMPLE 1

A manganese (II) sulfate solution containing 11.5 g of MnSO₄.4-5H₂ O in200 ml of the solution was prepared and L-ascorbic acid was dissolved inthe solution in amounts of 0 to 8.80 g, based on 200 ml of the solution,to prepare various solutions containing differing manganese (II)composition.

A water-absorbent paper (20 g) of size 255 mm×80 mm×13 mm and ahoneycomb-like structure was impregnated with each of the so-preparedsolutions to obtain impregnated papers. Then the impregnated papers wereair-dried to cause the composition to be carried on the paper in anamount of 43 to 52 percent by weight based on the weight of the paperand the dry solids content. Each impregnated paper was suspended in atest box having a volume of 0.12 m³, and then gas having an ammoniaconcentration of about 200 ppm was circulated in the box at a rate of1.2 m³ /min. The concentration of ammonia in the box after ten minuteswas measured as an initial concentration, and that after thirty minuteswas measured as a residual concentration. The results are shown in FIG.1.

As is apparent from the results in FIG. 1, it is indicated that thecomposition consisting of only manganese (II) sulfate failed to exhibita satisfactory reactivity to ammonia, but the composition in whichascorbic acid coexists was increased in reactivity. More specifically,the addition of ascorbic acid in an amount as small as 0.1 mol causedthe ammonia-removing function of the composition to be improved. Suchimprovement was noteworthy when ascorbic acid was added in an amount of0.29 to 0.75 mol.

EXAMPLE 2

A manganese (II) sulfate solution containing 11.5 g of MnSO₄.4-5H₂ O in200 ml of the solution was prepared as in Example 1. Then, L-ascorbicacid was added to the solution in an amount of 0.5 mol, based on mol ofmanganese, to prepare a solution (Solution A). To Solution A was addedcitric acid, which is an oxypolybasic acid, in amounts 0-1.25 mol basedon manganese to prepare a series of solutions varying citricacid-concentration (A series). Concurrently, an aqueous solutioncontaining only manganese (II) sulfate (Solution B) was prepared, andthen citric acid was added thereto in amounts of 0-1.25 mol, based onmanganese to prepare another series (B series) of solutions of varyingconcentration of citric acid. Then a honeycomb-like water absorbentpaper was impregnated with each of the so-prepared solutions andair-dried, to obtain impregnated papers as in Example 1.

A deodorizing test was carried out using an apparatus and underconditions similar to Example 1, except that the initial ammoniaconcentration was set at 400 ppm which is twice that used in Example 1,because it was expected that more amount of ammonia would be adsorbedcompared with Example 1. The results are shown in FIG. 2, which clearlyindicates that the coexistence of ascorbic acid exhibited satisfactoryeffects at a region in which the amount of addition of thecomplex-forming agent to manganese (II) is small, resulting in theammonia-removing ratio of the composition to be highly improved comparedwith that obtained due to the ammonia-neutralizing effect of citricacid.

EXAMPLE 3

11.5 g of manganese (II) sulfates tetra- or hepta-hydrate and 4.4 g ofascorbic acid (a molar ratio of 0.5 to manganese) were added to anddissolved in 200 ml of water, and then 5.25 g of citric acid was addedthereto to obtain a 20% active manganese (II) aqueous solution. Thesolution was stored, in place of water, in an ultrasonic humidifier (100V, 45 W, manufactured by Koshin Co. (Japan)) so that the humidifier wasused as an atomizer for atomizing the active manganese (II) solution.Then the atomizer was placed in a closed container of size 500 mm×900mm×480 mm and volume 0.22 m³ equipped with an internal agitating fan,and then hydrogen sulfide gas of a predetermined concentration was fedinto the container at a rate of 1.8 m³ /min to carry out a contactreaction between the atomized active manganese (II) solution and thehydrogen sulfide gas in the container, during which treated gas wasdischarged from the container through an outlet, and the concentrationof hydrogen sulfide in the gas was measured. The operation was carriedout while setting the indicator of the humidifier at a maximum value "9"on the scale, which means that the rate of consumption of the solutionwas about 40 ml/hr.

The operation was continuously carried out for eight hours, wherein theinitial concentration of hydrogen sulfide was set at 1800 ppm, 900 ppm,and 350 ppm, and the concentration of hydrogen sulfide at the outlet isshown an average value.

    ______________________________________                                        Initial Concentration                                                                      Outlet Concentration                                                                         Removal Ratio                                     of H.sub.2 S (ppm)                                                                         of H.sub.2 S (ppm)                                                                           (%)                                               ______________________________________                                        1800         67.5           96.1                                               900         20.1           97.7                                               350          0.0           100.0                                             ______________________________________                                    

Thus, it will be noted that the composition of the present inventionsubstantially completely treat hydrogen sulfide gas having an initialconcentration as high as 500 ppm.

Having described our invention as related to the embodiment, it is ourintention that the invention not be limited by any of the details of thedescription, unless otherwise specified, but rather be construed broadlywithin its spirit and scope as set out in the accompanying claims.

What I claim is:
 1. A method for deodorizing using an oxidation resistant divalent manganese ion composition which comprises contacting an odorous gas with a divalent manganese ion composition, said divalent manganese ion composition comprising a divalent manganese ion having an acid component bonded thereto, wherein said acid component is at least one member selected from the group consisting of ascorbic acid, citric acid and salts thereof; andwherein the molar ratio of said acid component to said divalent manganese ion is in the range of 0.1:1 to 1:1.
 2. The method according to claim 1, wherein the divalent manganese ion comes from a compound selected from the group consisting of manganese (II) chloride, manganese (II) nitrate, manganese (II) sulfate, manganese (II) acetate, and manganese (II) thiocyanate.
 3. The method according to claim 1, wherein the composition is in a solid form.
 4. The method according to claim 1, wherein the composition is carried on a porous substrate.
 5. The method according to claim 1, wherein said acid component consists of ascorbic acid, salts thereof, or mixtures thereof.
 6. The method according to claim 1, wherein said acid component consists of citric acid, salts thereof, or mixtures thereof.
 7. The method according to claim 1, wherein said acid component comprises (1) citric acid or a salt thereof and (2) ascorbic acid or a salt thereof. 